As a method to provide an attractive appearance for synthetic resins, a method for kneading powder of woods in synthetic resins has been applied; however, since the compatibility between synthetic resins and woods is generally poor, the filling rate of wood in most commercial molding materials filled with wood powder currently remains slightly exceeding 50% by weight.
The conventional methods for producing molding materials filled with wood powder are called a simple mixing method, and composed of the following steps; employing powder of wood such as cedar, white cedar, pine and the like of which the water content is equal to or less than 12% after being subjected to an artificial drying processing and of which the grain size is approximately 150 μm, introducing such wood powder in an amount of 50% by weight into a mixing and melting device heated at approximately 160° C. by heated steam or oil, drying for approximately 20 minutes by rotating mixing blades to reduce the water content to be equal to or less than 0.3%; adding, thereafter, a binder of thermoplastic resins (such as PPs, PEs or biodegradable resins), a compatibility accelerator (such as reactive polyolefin-based oligomers or maleic anhydride) and the like in an amount of 50% by weight, followed by simply mixing for approximately 20 minutes by rotating the mixing blades. Then, a mixture formed in a gel state is introduced to a cooler (cooling water: 20° C., flow rate: 100 L/minute) to be cooled and pelletized by rotating the blades for approximately 15 minutes.
Any of the conventional methods employ commercial wood powder, and individually apply a drying step, mixing and melting step, and pelletizing step in their production. These methods are not concerned with water content of materials employed; if the materials are being chipped, they do not combine all steps of pulverizing, drying, melting and mixing, and pelletizing, into one step (only with one mixing and melting device); are also impossible to carry out within a short thermal history; release an environmental load in reusing wasted materials, and have problems with production costs and productivity.
The present invention also provides methods for utilizing or reusing materials which are problematic for conventional methods in terms of cost and productivity, the materials such as chipped woody waste materials or woody waste materials like pruned branches and leaves of trees, plant materials and plant-waste materials like stems and leaves of wheat; and enhances utilization of wasted materials and promotes reuse thereof by improving the filling ratio.